1. Field of the Invention
The present invention relates to an oil-type one-way damper for producing a braking action with respect to a lid during either opening or closing thereof.
2. Description of the Prior Art
Oil-type dampers are widely used in, for example, audio and video tape recorders in order to effectively reduce vibration and shock produced when a cassette tape holder is projected outward from the recorder from its initially retracted position so that smooth motion of the holder is obtained. Such an oil-type damper is disclosed in, for example, U.S. Pat. Nos. 3,861,503, 3,882,976, 4,342,135 and 4,426,752. In all of the dampers disclosed in these U.S. patents, a rotor is rotatably incorporated in a housing of the damper and a clearance between the housing and the rotor is filled with oil so that rotational motion of the rotor is regulated by the resistance resulting from the viscosity of the oil. In the Japanese Utility Model Public Disclosure No. SHO 58-189843, the present inventor has proposed a damper having a housing in which a soft and flexible diaphragm with good resiliency is incorporated together with a rotor so that the thermal expansion of the oil contained in the housing is absorbed by the flexible diaphragm, whereby the oil is prevented from leaking out of the housing.
However, in this type of damper, since the resilient force of a spring or the like is used only for projecting the cassette tape holder from the main body of the recorder, it is necessary for the damper to apply a braking action to the holder only when the holder is being urged outwardly by the spring while such braking action is neither required or desirable when the holder is being pushed inward against the spring. More specifically, since the user has to push the holder by hand when retracting it into the main body of the recorder, if the braking action is also effective at a time when the holder is pushed into the main body of the recorder, the user is undesirably required to exert a larger pushing force on the holder than when no braking is applied.
Thus, is some cases, it is preferable that the braking action be effective in only one direction of movement and not be effective in the other so that resistance to movement in the other direction is reduced as much as possible. However, in the conventional oil-type damper, such braking action is effective in both the normal and the reverse directions of rotation of the rotor. This is a defect inherent in the conventional damper.